1. Field of the Invention
The present invention relates to a color selecting mechanism for a cathode ray tube for use in a color television receiver, various display devices and so on, for example.
2. Description of the Prior Art
For example, a color selecting mechanism 42 called an aperture grill, as shown in FIG. 1, is known as a color selecting mechanism for a color cathode ray tube. This color selecting mechanism 42 is constructed in a manner that it has a frame 41 constituted by opposite support members (long-side portions) 41a and U-shaped elastic members (short-side portions) 41b provided between the end portions of the opposite support members 41a, and that a color selecting electrode 35 having a number of longitudinal stripe aperture portions 35a is stretched over the support members 41a of this frame 41. In the color selecting electrode (so-called grid structure) 35, a number of slit aperture portions 35a are arranged so as to be in parallel to each other so that a slender stripe grid element 35b is formed between each pair of adjacent ones of the aperture portions 35a.
It is preferable that the ratio I.sub.1 /I.sub.2 of the sectional secondary moment I.sub.1 of the support members 41a of the frame 41 in the tension direction of the grid elements 35b, that is, in the direction to give turnbuckle, to the sectional secondary moment I2 of the elastic members 41b in the same manner, is selected to be 1.5 to 2.0, more preferably 1.70 to 1.80 (see Japanese published patent publication No. 61-31583).
On the other hand, such an integrated type color selecting mechanism 30 as shown, for example, in FIG. 2 has been proposed in order to reduce a strain at the time of working to thereby increase the accuracy of the dimension, and in order to simplify the working process.
As shown in FIG. 2, this color selecting mechanism 30 is molded integrally by use of the same material so that a rectangular frame 33 is constituted by long-side portions 31 and short-side portions 32.
Both of the long-side frames 31 and the short-side frames 32 are formed so as to be L-shaped in section, and their upper surfaces 31a and 32a are substantially in the same plane. Further, connection portions 34 between the long-side frames 31 and the short-side frames 32 respectively have curvature portions depending on the thickness of the frame 33, and cut portions 32b are formed in the respective short-side frames 32 so as to ensure the elasticity when the color selecting electrode 35 is to be attached. Then, the color selecting electrode 35 having a number of longitudinal stripe aperture portions 35a is stretched over the upper surface of the frame 33 (see Japanese published patent publication No. 60-6066).
However, in the case of such a conventional example, since the respective upper surfaces 31a and 32a of the long-side frames 31 and the short-side frames 32 are substantially on the same plane as shown in FIG. 2, it is necessary for the connection portions 34 between the long-side frames 31 and the short-side frames 32 to have a certain curvature depending on the thickness of the frame 33.
On the other hand, since the color selecting electrode 35 is attached, by welding, to the upper surfaces 31a of the long-side frames 31, there has been a disadvantage that the longitudinal dimension of the color selecting electrode 35 is limited so that it is impossible to ensure an enough area for a so-called effective screen.